A low-rate wireless personal area network (LR-WPAN) refers to a set of devices that communicate with each other within an area using a same wireless channel and in compliance with the Institute of Electrical and Electronics Engineers (IEEE) 802.15.4 standard, and the LR-WPAN is also referred to as an IEEE 802.15.4 network. The IEEE 802.15.4 standard defines a physical layer and Media Access Control in the LR-WPAN.
Based on communication capabilities, devices in the LR-WPAN are classified into a full-function device (FFD) and a reduced-function device (RFD). Communication can be directly performed between FFDs or between an FFD and an RFD, but cannot be directly performed between RFDs. An RFD can communicate only with an FFD, and forwards data using an FFD. In each LR-WPAN, at least one FFD is required to serve as a network coordinator. In addition to direct participation in applications, the coordinator is also responsible for tasks in the LR-WPAN, such as member identity management, link status information management, and packet forwarding. An RFD is mainly used for relatively simple applications, for example, a light switch and a passive infrared sensor. The RFD needs to transmit a relatively small volume of data, and occupies few transmission resources and communication resources. Therefore, a low-cost implementation solution can be used for the RFD.
To satisfy an energy-saving requirement, generally, each time after a low power-consumption RFD hibernates for a period, the RFD starts a quite short running time window for running. The RFD enters a hibernation state again if not receiving a wake-up packet within a running time window. For example, the RFD hibernates for 5 minutes, and then runs for 100 milliseconds, that is, hibernation duration is 5 minutes, and a running time window is 100 milliseconds. The RFD hibernates for 5 minutes and runs for 100 milliseconds, and then hibernates for 5 minutes and runs for 100 milliseconds in a periodical manner. If control needs to be performed on the RFD, for example, upgrading or data querying, the RFD needs to be woken up before the RFD runs. Conventional wake-up mechanisms include the following two types.
Wake-up in unicast mode: A coordinator sends a unicast frame to wake up an RFD that needs to be controlled. Because of a quite short running time window of an RFD, it cannot be ensured that one RFD can be woken up after a unicast frame is sent once. The coordinator may wake up one RFD only after sending a unicast frame for multiple times. If a relatively large quantity of RFDs need to be controlled, a quite long time may be taken, and wake-up efficiency is rather low.
Wake-up in broadcast mode: A coordinator sends a broadcast frame to wake up a device. Because all devices share a channel, all the devices in an LR-WPAN can receive the broadcast frame sent by the coordinator, and need to respond to the broadcast frame. In an LR-WPAN using a star networking mode, a response conflict between broadcast frames is easily caused. Therefore, the coordinator cannot receive a response from an RFD that needs to be controlled, and an RFD that does not need to be controlled may also be woken up. As a result, power consumption is increased, and energy-saving cannot be achieved.